When electrical power distribution techniques were first being developed, little was known about the current carrying capacity of copper wire, voltage drop, line loss and many other aspects of electrical power distribution. The availability and cost of copper wire was a major consideration. Thomas Edison and his engineers developed a means of power distribution that required twenty-five percent less wire than any other then known method. Essentially, two circuits could be distributed using only three wires by using a common wire. Over 100 years later, the "Edison Circuit" remains as the standard for power distribution. Single-phase transformers with a center tap output terminal are designed for this purpose. A circuit wire originating from the center tap is used as the common wire for two circuits. For safety reasons, the center tap is also used as the reference point from which the grounding system originates. Many interference problems are attributable to the neutral-to-ground connection made at the center tap. Because of impedance in alternating current ("ac") circuits, not all of the power flows directly back to its source. Some power is changed into noise in one form or another, escapes from the neutral wire into the ground reference and causes interference or malfunction in the operation of electronic equipment. Two-wire output (noncenter tapped) 120 volt isolation transformers and 120/208 volt three-phase 4-wire systems are similarly neutral-to-ground referenced and also exhibit such noise problems.
Harmonic distortion, reactive currents, power factor, radio frequency interference ("RFI"), electromagnetic interference ("EMI") are some of the many aspects of poor power quality and interference in problem situations. Active power conditioning is the one possible way to address the most serious of these problems. Micro-processor based power factor correction, micro-processor based anti-harmonic noise, true sinewave inverters and similar sophisticated technology are proposed to solve the problems. The technology is very sophisticated and is rapidly advancing. The one underlying theory behind all of this technology is that problems manifest themselves in electronics when stray current in the neutral wire escapes from the circuit and flows into the ground wires where there is a network of paths that lead into signal circuitry. This is called an eddy current and is one of the ways noise can get into electronic signals. If the reactive power elements can be cleaned up and the power signal made more efficient, eddy currents can be avoided.
Improved grounding system designs have been developed in an attempt to reduce noise in the reference source. For example, a "Linear Signal Reference Grid" may be used to attempt to handle ground loops and balance chassis potentials. An impedance of 0.1 ohms is the recommended standard. But since reactive currents are most of the problem, lowering impedance only facilitates greater current flow. Much reactivity occurs directly between the voltage source and the ground reference itself (in normal mode) in balanced power supplies and balanced filter circuits which has little to do with neutral wires, inter-chassis potentials or how a grounding circuit is constructed. Reducing chassis-to-chassis potentials does little to prevent some reactive currents from saturating the grounding grid and gaining access into high impedance signal circuits through the reference. The high impedance path in most of these signal circuits is an inductor, a low level signal input transformer. Induction causes some of the reactive current to be realigned with its lagging voltage phase only to reappear as noise in the program signal. Hum bars on a video monitor are one manifestation of this phenomenon.
In modern electronic applications in normal mode or in the more customary "differential" mode of operation where there is a "hot" wire a "neutral" wire and a "grounding" conductor, there is a two-way relationship between the voltage signal and reference potential with the reference positioned at one extremity. In the analogous art of electronics, this is called a "single-ended" or "unbalanced" circuit. The consequences of this single-ended, two-way relationship between the voltage signal and the ground reference become clearly apparent when reactive power artifacts originating from the load appear in the neutral wire. The reference source of a reactive power artifact on the neutral is rotated one hundred and eighty degrees from the neutral at the "hot" side of the power circuit where the load is connected so as to be opposite the original reference. Not all of the reactive current on the neutral wire flows back to its source because of impedance across the power system's transformer. Some of it is left on the line. There are also other types of power artifacts and grounding system noises which originate at the load. By design, there was to be but one reference point, now there are at least two. The complexities that this situation presents where there are multiple and various types of loads are so great as to have been unsatisfactorily resolved by the above-mentioned prior art methods and devices.